Various mechanisms are known to facilitate the cleaning and maintenance of dies used for the extrusion of polymer materials, while minimizing down time. Molten polymers are extruded through dies to form films, strands, nonwoven webs, and other finished polymer forms. As polymer exits the die, some of the polymer clings to the die openings or "lips," accumulating on the exterior surface of the die. This die lip build-up gradually increases until it accumulates to a point where it breaks off, possibly causing a defect in the product. Considerable engineering goes into the design of dies to minimize this build-up. Diverging, converging, radiused, and angled die lip geometries all are examples of methods developed to minimize this build-up. However, no die design completely eliminates it. It is common practice to temporarily halt the extrusion operation to perform maintenance on the die to remove this build-up.
U.S. Pat. No. 5,435,708, issued to Kaun, discloses a melt blowing die head with opposing die lips mounted on lip guides pivotally connected to respective setback bars. To facilitate cleaning and maintenance of the die, the lips can be swung away from the spinnerette on the respective lip guides. This allows for reduced down time during maintenance of the die, but does not permit maintenance during operation of the line.
U.S. Pat. No. 5,720,986, issued to Gohlisch et al., discloses an extrusion head having a stationary part fixed on an extrusion installation. The installation includes a plurality of extrusion cylinders. The stationary part has flow channels, each in communication with a respective extrusion cylinder and a common extrusion die. Two pivotal outer parts hinged on the stationary part are selectively swingable individually between open and closed positions. The outer parts define an extrusion orifice for the die in their closed position. When the outer parts are opened, maintenance can be performed on the die.
U.S. Pat. No. 4,413,973, issued to Peters, discloses a die which has a removable extrusion plate covering the die head. The plate can be removed and replaced to minimize down time required for maintenance.
A common feature of the prior art devices is that routine cleaning and maintenance requires at least some down time. While efforts have been made to simplify maintenance and reduce down time, no device has allowed maintenance to be performed while the extrusion operation is ongoing.